The present invention is generally related to radiotelephones, and more particularly to an apparatus and method for detecting and powering a headset accessory for cellular radiotelephones.
Conventional portable cellular radiotelephones may be coupled to a variety of accessories including different size batteries as illustrated in U.S. Pat. Nos. 5,164,652 and 5,237,257, an auxiliary battery as illustrated in U.S. Pat. No. 5,684,384, an external power adapter as illustrated in U.S. Pat. No. 5,506,490, a power booster as illustrated in U.S. Pat. No. 4,636,741, and a headset. The presence of the foregoing accessories may be determined by detecting resistors of a predetermined value or by detecting an electrical signal ground or predetermined voltage on an input signal. Many of these accessories are mounted in a vehicle where they can be powered from the vehicle's battery. However, when a vehicular power source is not available, there is a need for powering an accessory directly from a radiotelephone.